1. Field of the Invention
The present invention relates to a backlight module, and more specifically, to a backlight module capable of dynamically adjusting brightness.
2. Description of Prior Art
A backlight module is a key component of a liquid crystal display (LCD). For the liquid crystal fails to shine itself, the purpose of the backlight module is to provide backlight by means of a light source with sufficient brightness and even distribution, wherein the light source emits light into an optics-mechanism to simply and effectively spread as a planar light surface with high luminance and uniform brightness. Because the LCD is widely used in various electronic products such as a monitor, a notebook computer, a digital camera, and a projector, especially a high growth of the notebook and the LCD monitor using large-size LCD panels, the demand for the backlight module has increased tremendously.
The liquid crystal display (LCD) comprises a light source (e.g., light-emitting diode, LED), a reflector, a light guide plate, a diffusion sheet, a brightness enhancement film (BEF), and a liquid crystal panel. Firstly, the light emitted from the light source enters the light guide plate. The diffusing structure disposed at the bottom surface of the light guide plate guides the light to become a uniformly distributed planar light source. Next, the reflector at one side of the light guide plate reflects the light emitted to the reflector back to the light guide plate to avoid the leakage of the light and to increase the efficiency of light utilization. Next, the light emitted from the light guide plate undergoes a uniform lighting effect of the diffusion sheet and a light-gathering effect of the BEF to enhance the brightness and uniformity of the light source. Finally, the light is emitted into the liquid crystal panel.
The light guide plate is a wedge-shaped plate with a glossy surface. The bottom surface comprises diffusing structures on which a circular or square shape is engraved. A great amount of light is reflected by the reflector and conducted towards a thin end. When light hits the diffusing structure of the bottom surface, the reflected light will spread out all over, destroy the total internal reflection, and emit from the front surface of the light guide plate. The light guide plate radiates light uniformly owing to the diffusing structure with pictures of various densities and sizes.
The brightness of the light guide plate is mainly determined by the brightness of light generated by a light source. The backlight module is capable of adjusting luminance to reduce power consumption. However, for a light source on one side of the light guide plate, it is difficult to locate an illumination target region distant from light source precisely when the light source undergoes dimming. As for light sources on a two sides of the light guide plate, the brightness of the two adjacent regions is influenced by each other's light sources at both sides when the light source undergoes dimming.